| 1 | #ifndef _URCU_FUTEX_H |
| 2 | #define _URCU_FUTEX_H |
| 3 | |
| 4 | /* |
| 5 | * urcu-futex.h |
| 6 | * |
| 7 | * Userspace RCU - sys_futex/compat_futex header. |
| 8 | * |
| 9 | * Copyright 2011-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 10 | * |
| 11 | * This library is free software; you can redistribute it and/or |
| 12 | * modify it under the terms of the GNU Lesser General Public |
| 13 | * License as published by the Free Software Foundation; either |
| 14 | * version 2.1 of the License, or (at your option) any later version. |
| 15 | * |
| 16 | * This library is distributed in the hope that it will be useful, |
| 17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 19 | * Lesser General Public License for more details. |
| 20 | * |
| 21 | * You should have received a copy of the GNU Lesser General Public |
| 22 | * License along with this library; if not, write to the Free Software |
| 23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 24 | */ |
| 25 | |
| 26 | #include <urcu/config.h> |
| 27 | #include <errno.h> |
| 28 | #include <stdint.h> |
| 29 | #include <time.h> |
| 30 | |
| 31 | #ifdef __cplusplus |
| 32 | extern "C" { |
| 33 | #endif |
| 34 | |
| 35 | #define FUTEX_WAIT 0 |
| 36 | #define FUTEX_WAKE 1 |
| 37 | |
| 38 | /* |
| 39 | * sys_futex compatibility header. |
| 40 | * Use *only* *either of* futex_noasync OR futex_async on a given address. |
| 41 | * |
| 42 | * futex_noasync cannot be executed in signal handlers, but ensures that |
| 43 | * it will be put in a wait queue even in compatibility mode. |
| 44 | * |
| 45 | * futex_async is signal-handler safe for the wakeup. It uses polling |
| 46 | * on the wait-side in compatibility mode. |
| 47 | * |
| 48 | * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted |
| 49 | * (returns EINTR). |
| 50 | */ |
| 51 | |
| 52 | extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 53 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); |
| 54 | extern int compat_futex_async(int32_t *uaddr, int op, int32_t val, |
| 55 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); |
| 56 | |
| 57 | #ifdef CONFIG_RCU_HAVE_FUTEX |
| 58 | |
| 59 | #include <unistd.h> |
| 60 | #include <errno.h> |
| 61 | #include <urcu/compiler.h> |
| 62 | #include <urcu/arch.h> |
| 63 | |
| 64 | static inline int futex(int32_t *uaddr, int op, int32_t val, |
| 65 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 66 | { |
| 67 | return syscall(__NR_futex, uaddr, op, val, timeout, |
| 68 | uaddr2, val3); |
| 69 | } |
| 70 | |
| 71 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 72 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 73 | { |
| 74 | int ret; |
| 75 | |
| 76 | ret = futex(uaddr, op, val, timeout, uaddr2, val3); |
| 77 | if (caa_unlikely(ret < 0 && errno == ENOSYS)) { |
| 78 | /* |
| 79 | * The fallback on ENOSYS is the async-safe version of |
| 80 | * the compat futex implementation, because the |
| 81 | * async-safe compat implementation allows being used |
| 82 | * concurrently with calls to futex(). Indeed, sys_futex |
| 83 | * FUTEX_WAIT, on some architectures (mips and parisc), |
| 84 | * within a given process, spuriously return ENOSYS due |
| 85 | * to signal restart bugs on some kernel versions. |
| 86 | */ |
| 87 | return compat_futex_async(uaddr, op, val, timeout, |
| 88 | uaddr2, val3); |
| 89 | } |
| 90 | return ret; |
| 91 | |
| 92 | } |
| 93 | |
| 94 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 95 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 96 | { |
| 97 | int ret; |
| 98 | |
| 99 | ret = futex(uaddr, op, val, timeout, uaddr2, val3); |
| 100 | if (caa_unlikely(ret < 0 && errno == ENOSYS)) { |
| 101 | return compat_futex_async(uaddr, op, val, timeout, |
| 102 | uaddr2, val3); |
| 103 | } |
| 104 | return ret; |
| 105 | } |
| 106 | |
| 107 | #elif defined(__FreeBSD__) |
| 108 | |
| 109 | #include <sys/types.h> |
| 110 | #include <sys/umtx.h> |
| 111 | |
| 112 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 113 | const struct timespec *timeout, |
| 114 | int32_t *uaddr2 __attribute__((unused)), |
| 115 | int32_t val3 __attribute__((unused))) |
| 116 | { |
| 117 | int umtx_op; |
| 118 | void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL; |
| 119 | struct _umtx_time umtx_timeout = { |
| 120 | ._flags = UMTX_ABSTIME, |
| 121 | ._clockid = CLOCK_MONOTONIC, |
| 122 | }; |
| 123 | |
| 124 | switch (op) { |
| 125 | case FUTEX_WAIT: |
| 126 | /* On FreeBSD, a "u_int" is a 32-bit integer. */ |
| 127 | umtx_op = UMTX_OP_WAIT_UINT; |
| 128 | if (timeout != NULL) { |
| 129 | umtx_timeout._timeout = *timeout; |
| 130 | umtx_uaddr = (void *) sizeof(umtx_timeout); |
| 131 | umtx_uaddr2 = (void *) &umtx_timeout; |
| 132 | } |
| 133 | break; |
| 134 | case FUTEX_WAKE: |
| 135 | umtx_op = UMTX_OP_WAKE; |
| 136 | break; |
| 137 | default: |
| 138 | errno = EINVAL; |
| 139 | return -1; |
| 140 | } |
| 141 | |
| 142 | return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr, |
| 143 | umtx_uaddr2); |
| 144 | } |
| 145 | |
| 146 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 147 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 148 | { |
| 149 | return futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 150 | } |
| 151 | |
| 152 | #elif defined(__CYGWIN__) |
| 153 | |
| 154 | /* |
| 155 | * The futex_noasync compat code uses a weak symbol to share state across |
| 156 | * different shared object which is not possible on Windows with the |
| 157 | * Portable Executable format. Use the async compat code for both cases. |
| 158 | */ |
| 159 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 160 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 161 | { |
| 162 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 163 | } |
| 164 | |
| 165 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 166 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 167 | { |
| 168 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 169 | } |
| 170 | |
| 171 | #else |
| 172 | |
| 173 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 174 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 175 | { |
| 176 | return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3); |
| 177 | } |
| 178 | |
| 179 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 180 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 181 | { |
| 182 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 183 | } |
| 184 | |
| 185 | #endif |
| 186 | |
| 187 | #ifdef __cplusplus |
| 188 | } |
| 189 | #endif |
| 190 | |
| 191 | #endif /* _URCU_FUTEX_H */ |